The teachings presented herein relate generally to calibration of output devices. The teachings presented herein relate more specifically to calibration of color displays.
An ever increasing number of presentations today are given electronically using projection display technology. However, in such presentations, color images often do not reproduce correctly due to lack of projector calibration. In cases where the color imagery is intended to convey an important message, this problem can severely diminish the value of a presentation. Examples include technical, educational, and marketing presentations attempting to demonstrate color and image quality effects. Readability of text and other details are often compromised as well, and often the presenter is compelled to apologize, insisting, “It looked good on my computer screen.”
A standard approach for determining the projector's tone response is to make device-independent measurements of R, G, B ramps with a spectroradiometer, and then derive a tone response function that relates digital input value to luminance by fitting or interpolating the measured data. This type of approach can be expected to produce a highly accurate correction. However, making spectroradiometric measurements is a very expensive, time-consuming and tedious process. Indeed this is the reason why projection display calibration is typically avoided, and users simply live with and otherwise tolerate the erroneous result.
What is needed is a straight forward easy to perform calibration for projection displays which does not require expensive test equipment or special involved operator skills or training to accomplish.
Disclosed in embodiments herein is a system for color correction, comprising an output device to be color corrected; a target of patches of known input values displayed on the output device; a digital camera capturing an image of the target of patches as rendered by the output device and providing image signals representative of the captured image of the target of patches; and a software calibration tool receiving the provided image signals and deriving a tone response calibration for the output device from a comparison of the provided image signals and the known input values.
Further disclosed in embodiments herein is a system for color correction of a display device, comprising a target of patches of known input values displayed on the display device; a digital camera capturing an image of the target of patches as displayed by the display device thus providing image signals representative of the captured image of the target of patches; and a software calibration tool receiving the provided image signals, from which the software calibration tool extracts calibrated camera signals, to thereby derive a tone response calibration for the display device by a comparison of the extracted calibrated camera signals and the known input values.
Further disclosed in embodiments herein is a system for color correction of a digital projection display with a digital camera, comprising a target of patches of known input values displayed on the digital projection display that the digital camera captures as displayed by the digital projection display and which the digital camera provides as image signals representative of the captured image of the target of patches. The system further comprises a processor receiving from the digital camera the image signals representative of the captured image of the target of patches, and a calibration tool resident on the processor that extracts calibrated camera signals from the image signals representative of the captured image of the target of patches, and thereby derives a tone response calibration for the digital projection display by a comparison of the extracted calibrated camera signals and the known input values.